Analysis of the Hydrogeological Conditions and the Effects of Development on the Hydraulic Head at Redmond Ridge East

Redmond Ridge East (RRE) is a large-scale master plan community in East King County, WA. In this report, I evaluate the spatial variability of the Quaternary Advance Outwash (Qva) at RRE and the time-series data for 16 water wells with the intent to better understand groundwater below the RRE area. I investigate changes between pre- and post-development conditions through the determination of temporal changes in annual water level, annual water level fluctuations, hydraulic head response to precipitation, and ambient drainage of the aquifer. I also perform a basic analysis of the annual aquifer recharge and a determination for the storage through the implementation of the water table fluctuation (WTF) method. Associated Earth Sciences (AESI) was tasked with monitoring the geological and environmental impacts during the development of RRE and collected the data I use in this report. AESI involvement in monitoring began in 1998 and extends to the present. Sixteen wells were identified in the RRE area with adequate temporal data to conduct the analysis. A comparison of the well logs and aquifer testing data allowed local variations in the Qva to be mapped. The WTF was used to determine a range of reasonable specific yield values for locations where the Qva was unconfined. Yearly average of the seasonal water level high and lows, and the fluctuations were quantified. Temporal relationships were established through linear regression. The average water level was found to be increasing in some locations, and the corresponding fluctuations were found to decrease. However, no clear change between pre- and post-development was observed. The response of hydraulic head to precipitation was investigated through an analysis of hydrographs for ten wells. Periods of consistent response and the corresponding precipitation during each period were delineated. A linear relationship between precipitation and water level change was determined. The threshold precipitation under which there is a positive response in the hydraulic head was established. No observable changes were apparent between pre- and post-development conditions. The ambient drainage for the Qva was calculated using recessional periods on the hydrograph. The transmissivity of Qva varies with thickness of the overlying lodgment till and thickness of the Qva, itself. Water level fluctuations observed in the Qva are consistent with regional observations. Localized areas in the Qva display the large 10 foot fluctuations and these anomalies are likely due to a combination of the local variability in the storativity as well as the concentration and channeling of water due to geographical variations in the Qva and the overlying topography. All trends seen in the RRE area remained relatively constant through time. There was no evidence showing an effect of development on the hydraulic head at RRE. This implies that the style and distribution of infiltration has not changed as a result of development, and that any measures in place are properly mitigating the effects of development on the RRE region.

River and Hillslope Response to Localized Uplift Along a Left Bend of the San Andreas Fault, Santa Cruz Mountains, CA

Studying landscape evolution of the Earthís surface is difficult because both tectonic forces and surface processes control its response to perturbation, and ultimately, its shape and form. Researchers often use numerical models to study erosional response to deformation because there are rarely natural settings in which we can evaluate both tectonic activity and topographic response over appropriate time scales (103-105 years). In certain locations, however, geologic conditions afford the unique opportunity to study the relationship between tectonics and topography. One such location is along the Dragonís Back Pressure Ridge in California, where the landscape moves over a structural discontinuity along the San Andreas Fault and landscape response to both the initiation and cessation of uplift can be observed. In their landmark study, Hilley and Arrowsmith (2008) found that geomorphic metrics such as channel steepness tracked uplift and that hillslope response lagged behind that of rivers. Ideal conditions such as uniform vegetation density and similar lithology allowed them to view each basin as a developmental stage of response to uplift only. Although this work represents a significant step forward in understanding landscape response to deformation, it remains unclear how these results translate to more geologically complex settings. In this study, I apply similar methodology to a left bend along the San Andreas Fault in the Santa Cruz Mountains, California. At this location, the landscape is translated through a zone of localized uplift caused by the bend, but vegetation, lithology, and structure vary. I examine the geomorphic response to uplift along the San Andreas Fault bend in order to determine whether predicted landscape patterns can be observed in a larger, more geologically complex setting than the Dragonís Back Pressure Ridge. I find that even with a larger-scale and a more complex setting, geomorphic metrics such as channel steepness index remain useful tools for evaluating landscape evolution through time. Steepness indices in selected streams of study record localized uplift caused by the restraining bend, while hillslope adjustment in the form of landsliding occurs over longer time scales. This project illustrates that it is possible to apply concepts of landscape evolution models to complex settings and is an important contribution to the body of geomorphological study.

Presynaptic Anchoring of PKA by AKAP7 is Required for Pattern Separation by Dentate Gyrus

Thesis (Ph.D.)--University of Washington, 2016-06